Transgenic and/or knock-in animals engineered for in vivo imaging often employ specific promoters capable of receiving various signals and converting those signals into transcriptional outputs.
However, many of such promoters suffer from overall weak induction levels to the point that signal to noise ratios are not sufficiently high to achieve good quality data. This can be especially problematic when the tissues in which a reporter functions is located deep within the animal's body. Furthermore, whole animal imaging that is based on luminescence or fluorescence can be stymied by signal interference that arises when a promoter has residual activity in a surrounding tissue such as skin. In certain cases, a residual expression level of 2-4% can be enough to hamper accurate results.
Certain aspects of this disclosure relate to a reporter system that can, in some embodiments, mitigate the drawbacks described above.